1. Field of the Invention
The present invention relates to a reinforcing structure of a printed circuit board and in particular to a electronic apparatus with a reinforcing structure for sustaining stress applied to a connection of a printed circuit board to electronic components mounted on the above printed circuit board by sustaining flexure of the above printed circuit board attached within a housing.
2. Description of the Related Art
There have been proposed and commercially available various kinds of electronic apparatuses with a printed circuit board fixed in a housing thereof, the printed circuit board having electronic components mounted thereon. In these electronic apparatuses, the printed circuit board is attached to the housing by aligning each threaded hole in the board respectively with a threaded hole in a pillar-shaped support member provided at each predetermined position on the inner surface of the housing and fixing them together with a screw. Therefore, when a small electronic apparatus such as a portable equipment having a housing made of molded plastics is dropped or a person sits down on the equipment put in a pocket of the trousers and the housing is deformed, stress directly acts on the printed circuit board inside to cause a bend in the above printed circuit board, the stress concentrating on soldered portions of the electronic components mounted on the above printed circuit board. Consequently, problems occur such as solder cracks, lands stripped off the printed circuit board or other failures. Such a failure often occurs in a component of a relatively large size and having a connection on its back side to a printed circuit board through solder bumps, such as BGA (Ball Grid Array) and CSP (Chip Size Package) in particular.
Conventionally, to prevent the failures mentioned above, a structure as shown in FIGS. 12 and 13 is employed. FIG. 12 is a perspective view showing the state in which printed circuit board 1 having electronic components 5 such as BGA-type bonded thereto with thermosetting resin 6 is attached to housing 2. FIG. 13 is a cross sectional view showing bonded portions with thermosetting resin 6.
Each of electronic components 5 has been bonded to a printed circuit board 1 by a thermosetting resin 6. By this, each electronic component 5 and its contact portions composed of lands 7 and solder bumps 8 are fixed to the printed circuit board 1, and protected from the failure due to the concentrated stress. For example, bonding with thermosetting resin 6 is performed by placing electronic components such as BGA-type on the printed circuit board and then applying a thermosetting resin such as epoxy resin around the electronic components and heating them.
Another approach to preventing the failure mentioned above is to employ a reinforcing structure as described in Japanese Patent Application Unexamined Publication No. 11-214806. This reinforcing structure is a structure to be attached to the housing with metallic reinforcing members respectively mounted along the both sides of the printed circuit board.
The conventional approach by which electronic components are bonded to the printed circuit board with a thermosetting resin has a problem that manufacturing cost becomes higher because it is necessary to provide equipment dedicated to applying and heating the thermosetting resin. In addition, when a defect is found in an electronic component after bonding to the printed circuit board, the electronic component concerned cannot be replaced solely, so the printed circuit board having the electronic components mounted thereon will be discarded. Consequently, a problem occurs that manufacturing yield is lowered and manufacturing cost becomes high.
In the reinforcing structure according to the Japanese Patent Application Unexamined Publication No. 11-214806 in which metallic reinforcing members are respectively bonded to the printed circuit board along the both sides of the printed circuit board, the printed circuit board is attached to the housing at the positions of the reinforcing members, so the metallic reinforcing members should be processed and a problem occurs that processing cost is necessary.
An object of this invention is to provide a printed circuit board reinforcing structure allowing flexure of the printed circuit board to be suppressed even if the board is thin or long and so flexible, thereby preventing failures such as solder cracks and lands stripped off the printed circuit board.
The above object is accomplished by an arrangement wherein a rod-like reinforcing member elongated along a longitudinal direction is comprised of: a groove into which one of both edges of the printed circuit board is to be fitted; a reinforcing rib which protrudes outwardly at a predetermined angle with respect to an opening direction of the groove portion and extends in a longitudinal direction of the reinforcing member; and a plurality of protrusions provided at positions, each of which corresponds to one of the supports of the housing to be fixed to a corresponding support so as to secure the reinforcing member to the housing.
The reinforcing member may be integrally formed of plastic. The reinforcing rib may protrude outwardly in a direction perpendicular to the opening direction of the groove portion.
The protrusions may be respectively provided on both ends of the reinforcing member in the longitudinal direction, wherein each of the protrusions protrudes in a direction opposite to the opening direction of the groove portion.
The protrusions may be respectively provided on both ends of the reinforcing member in the longitudinal direction, wherein each of the protrusions protrudes in the opening direction of the groove portion and is fixed to the corresponding support by means of a screw together with the edge of the printed circuit board fitted into the groove portion.
Side walls of the groove portion may be elastic and grasp the edge of the printed circuit board fitted into the groove portion by elasticity.
The electronic components may be mounted on the printed circuit board with solder bumps.